Bearing



y 1942- w. E. MCCULLOUGH 272833219 BEARING Filed Nov. 24, 1959 mmdm NH E C.T m H M, 2 Q

Patented May 19, 1942 UNITED STATES PATENT OFFICE sesame William E. McCullough, Detroit, Mich, assignor to Bohn Aluminum & Brass Corporation, Detroit, Mich., a corporation 01 Michigan Application November 24, 1939, Serial N?305,772 5 Claims. (Cl. 308-242) .This invention relates to an improved bearing ing which the 'supplyci oil is not fully availalloy and to an improved bearing structure. able. This situation is acute in airplane motors,

While the invention aims particularly to produce where the operative life of the engine depends a superior bearing of the interchangeable type largely on the performance of the bearings, and for use in aircraft engines, it can be applied 5 is particularly pressing in motors for military wherever bearings of the character produced are aircraft, which must survive power dives durserviceable. ing which the bearings are deprived of their A primary aim of the invention is to furnish usual full supp y of oil. 1 a bearing material which will support a rotating The present invention meets this situation by shaft without scoring even under abnormal conlining the bearings with an alloy of silver and ditions in which there is practically a total lack lead, silver predominating. Silver is oritself a of the normal supply of lubricant. This object good bearing material when properly lubricated, is accomplished by using as a lining material but tends to freeze to the shaft when lubrication silver-lead alloy, with silver predominant. fails. The softer lead appears to act as a lubri- Another object of the invention is to produce cant, since the addition of a relatively small a bearing structure in which the silver-lead linamount of lead greatly improves the performing is bonded to a stronger backing material ance of the bearing when running dry.

which supplies support and to whichthe lining It has been found that the proportions of silis firmly bonded by an alloy bond, the whole be-' vet and lead may be varied within fairly wide ing of such a nature that it is subject to a minlimits, according to the characteristics desired imum amount of heat distortion and is extremely in the bearing, although it is usually preferred resistant to corrosion. To meet these requireto have a predominance of silver. Since silver ments the backing is preferably formed of copis the harder of the two metals. the more silver I per-nickel alloy, as will be explained subsethe greater compressive strength the bearing quently. I will have. 0n the other hand, since lead is the These and other objects and advantages of the better material for dry running, the more lead invention will become apparent as the descripthe better the bearing will withstand abuse from tion proceeds. 7 lack of lubrication.

While preferred materials and forms are dis- In modern bearing practice standard interclosed herein for purposes of illustration, it changeable bearings have usually been produced should be understood that various changes may by supporting a thin lining of bearing metal on be made in materials and in arrangement of a backing of a stronger metal,- such as steel. parts without departing from the spirit of the The silver-lead bearing alloy cannot readily be invention. I bonded to either steel or aluminum bronze, and

This application is in part a continuation of the present invention provides a bearing conmy application Serial No. 231,101 filed Septemstruction in which the backing material is of h 22, 1938, such a nature'that the silver-lead alloy can be In th drawing firmly bonded to it and which presents other ad- Fig. 1 is a perspective view of a typical bearvantages. The preferred backing material is an ing to which the invention is applied. 40 alloy of 65% nickel'and 35% of copper, which Fig. 2 is a partial longitudinal section of the is commercially sold under the trade-mark bearing shown in Fig. 1. Monel metal.

Fig. 3 is a reproduction of a photomicrograph This nickel-copper alloy forms a good bond showing on a greately enlarged scale the grain with the silver-lead bearing alloy. In addition structure of a typical section taken on the same it has a coeflicient of heat expansion close to line as Fig. 2. that of the silver-base lining alloy, and hence One of the major problems in increasing the the combined structure is subjected to minimum life and efiiciency of modern high-speed mastresses and distortion due todiiferences in these chinery, especially internal combustion engines, coeflicients. Furthermore, the nickel-copper is to provide bearings of suflicient strength and alloy provides a wrought metal backing that has stamina. The bearings must not only give long physical properties superior to those of mild trouble-free service under normal operating steel; and which is strongly resistant to the acids conditions in which they receive a proper supply which often develop in the operation of interof oil, but they must be able to survive through nal combustion motors.

reasonably long periods of abnormal service dur- Up to the present time I have obtained best 2 1 I results with hearings in which the lining material is a silver-lead alloy containing from 1 to 7%% of lead, theremainder being substantially all silver. Tests have shown that lining alloys in this range form excellent bonds with the nickel and copper having similar properties but- A of proportions that will bond with the particular silver-lead alloy. It should be understood of course that any metal or alloy having suitable physical properties and having the ability to form a good bond with the preferred silver-lead alloymay be used for the backing material, and

that even with the silver-lead alloys containing up to '7 /2% of lead the proportions of nickel and copper may be varied somewhat from the 65-35 formula.

In manufacturing the bearing illustrated in Fig. 1 a suitable length of tubing of the nickelcopper alloy not specially treated and a quantity of the silver-lead alloy to which a small amount of sal ammoniacand naphtha were added, are heated together at 2000-2100 F. in a gas-fired furnace for approximately thirty minutes.' (Another advantage of the nickel-copper alloy is that it can be heated to a temperature above the melting point of silver, which is 1800" F., thus facilitating the formation of a good bond between the bearing alloy and the shell.) The liquid bearing alloy is then deposited on the inner wall of the tube by the well-known spinning process, during which the tube isrotated at 900 R. P. M. and then quickly cooled with a water spray while spinning. The tube may then be split longitudinally to form sections in and H and the bearing is finished to any desired form and dimensions.

In some types of bearings the tube is not split,

but is finished as a one-piece tubular hearing.

In the completed bearing the external shell or backing, indicated at I! in Figs. 2 and 3, supports a relatively thin lining II of the bearing alloy.

Fig. 3 is a reproduction of a photomicrograph of a part of the section shown in Fig. 2,.and illustrates the structure of the bearing alloy, in which the higher melting-point silver forms dendrites II, which are light-colored in the picture,

the spaces between the dendrltic branches being filled with the eutectic mixture of silver and lead, which shows as dark areas I! in the picture.

This figure also illustrates the type oi bond existing between the bearing layer l3 and the shell II. The dark layer, indicated at l8, between the bearing layer and the shell is made up of an alloy of the nickel-copper alloy with the silver lead alloy, the latter having penetrated along the boundaries of the nickel-copper alloy. This actual alloying of the bearing layer with the shell results from the fact that the bearing material is in the molten state when it is cast on the hot shell. a

While the preferred lining material is an alloy of silver and lead, small amounts of other metals such as cadmium, nickel or copper may be introduced to harden or otherwise modify the properties of the alloy.

Bearings made according to this invention have given very superior results in engines for military aircraft, and it will be clear to those skilled in the art that the invention can be used in other situations where similar bearing properties are desired.

I claim: Y

'1. In a bearing structure, a layer of bearing alloy comprising from 1 to l /2% of lead, the balance being substantially all silver.

2. In a bearing structure, a layer of bearing alloy comprising from 1 to 15% of lead, the balance being substantially all silver.

3. In a bearing structure, a layer of bearing alloy comprising from 1 to 30% of lead, the balance being substantially all silver.

4. A hearing structure comprising a backing lined with-a relatively thin layer of an alloy comprising silver to and lead 5 to 20%.

5. The. method of forming a bearing which comprises producin a molten silver-lead alloy with silver in the predominance, forming a sup-- port shell from an alloy comprising nickel and copper, heating the support shell to a temperature above the melting point of silver, and casting the molten silver-lead alloy against the hot support shell.

WILLIAM E. MCCULLOUGH. 

